/Engine/Plugins/Experimental/PCG/Source/PCG/Public/Elements/Metadata/PCGMetadataOpElementBase.h
First we need to gather all our input values. We use an index, starting at 0, and also use our empty struct to pack all our input types.
namespace PCG { namespace Private { namespace NAryOperation { template<typename... InputTypes, typename... Callbacks> bool PCG::Private::NAryOperation::Operation ( [FPCGMetadataElementBase::FOperationData](API\Plugins\PCG\Elements\Metadata\FPCGMetadataElementBase\FOperationData) & InOperationData, int32 StartIndex, int32 Range, const [Options](API\Plugins\PCG\Elements\Metadata\Options) & InOptions, const [TTuple](API\Runtime\Core\Misc\TTuple)< Callbacks... > & InCallbacks ) } } }